We have just managed to get GZIP working in IIS by adding the type

application/grpc-web

Inside of the httpCompression part of IIS. This correctly sets the Content-Encoding to gzip and we see a smaller footprint of the byte transfer. However, in ASP.NET we saw that one could also gzip the content of the data like this:

options.ResponseCompressionLevel = System.IO.Compression.CompressionLevel.Optimal;
options.ResponseCompressionAlgorithm = "gzip";

Which way is the most efficient in terms of data size? Or would it be equivalent to setting the gzip as above? One benefit of using the IIS gzip is that one can see the content clearly in developer console. If using the ASP.NET gzip the content is compressed also in the developer console.